Stock-Based Compensation - Plan Information (Details) - 2012 Plan - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
---|---|---|---|---|
Jun. 30, 2019 |
Jun. 30, 2018 |
Jun. 30, 2019 |
Jun. 30, 2018 |
|
Stock based compensation | ||||
Number of awards approved for grant (in shares) | 4,000,000 | 4,000,000 | ||
Common stock remaining available for issuance (in shares) | 680,623 | 680,623 | ||
Compensation expense | $ 2.5 | $ 2.5 | $ 5.0 | $ 4.8 |
Board of Directors | ||||
Stock based compensation | ||||
Common shares granted to members of board of directors as compensation for director services | 14,895 | 10,024 |